1. Field of the Invention
The invention relates to a method for manufacturing a casting-die body and to a casting-die body made of a hardenable copper alloy.
2. Description of Related Art
The casting die is one of the most important components of a continuous casting installation. The solidification of the melted mass begins in it. The principal design is generally composed of an external steel structure and the actual form-giving part of the casting die, the casting-die body. Today the casting-die body is almost exclusively made of copper or a copper alloy. The steel casing has the task of positioning the casting-die body and assuring the water circulation necessary for cooling.
The resistance to wear of copper alloys is relatively small. In particular, at the foot of the casting-die body, there is the danger of increased friction between the steel billet and the wall of the casting-die body as a result of differences between the casting-die body geometry and the shrinkage behavior of the steel, or as a result of insufficient guidance of the billet inside the casting die. Consequently, significant abrasion along with corresponding changes in shape of the casting-die body can occur.
For reasons of protection against wear, the casting-die body is therefore provided with an interior layer made of a wear-resistant material such as nickel or chromium. A casting-die body of this type having a wear-protective layer is found, for example, in German patent 31 42 196 C2. In this way, an improvement in the abrasion characteristics and thus an increase in the service life of the casting-die body can be achieved.
A chromium layer, in this connection, is distinguished by its greater hardness in comparison with nickel, and by its increased wear-protection, associated therewith. Therefore, an electroplated coating of the interior surface with hard chromium offers effective protection against wear.
However, due to the varying heat-expansion coefficients of the materials of the casting-die body and of the wear-protective layer, significant stresses arise in the wear-protective layer. As a result, the resistance to adhesion suffers and there is the danger of peeling or forming cracks.